JP2014174511A - Strobo device and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize a limit of a charge operation for protecting a circuit and the like from damage or degradation.SOLUTION: A strobo 20 emits light by accumulated electric charge of a capacitor 16. A charge circuit 12 charges the capacitor 16 every time the light is emitted by the strobo 20. During a charge period, a counter 28 is incremented by a first frequency-divided clock, and to the contrary, since the counter 28 is decremented by a second frequency-divided clock during a non-charge period, the counter 28 has a count value that reflects a ratio of the charge period. A controller 24 refers to the count value, and as the ratio of the charge period is higher, the controller 24 causes a next charge start timing of the capacitor 16 to be delayed. In this case, an amount of delay of the charge start timing is corrected according to a primary-side voltage Vbat of the charge circuit 12.

Description

  The present invention relates to a strobe device and a camera.

  In Patent Document 1 below, a capacitor for accumulating charges for causing a strobe to emit light, a charging means for charging the capacitor each time the strobe is emitted, and a ratio between a charging period and a non-charging period of the capacitor are determined. A strobe device is provided that includes a determination unit and a delay unit that delays the charging start timing of the capacitor as the ratio of the charging period increases based on the determination result of the determination unit. The increase in heat generated by the continuous light emission of the strobe causes destruction or deterioration of the circuit or the like, but this is appropriately prevented by limiting the charging operation due to the delay of the charging start timing.

JP 2005-216664 A

  In the strobe device as described above, when the charging condition of the capacitor changes, it is considered that the charging operation can be more appropriately restricted by controlling the charging start timing in accordance with the change.

  SUMMARY An advantage of some aspects of the invention is that it provides a strobe device and a camera that appropriately limit charging operations for protecting circuits and the like from destruction or deterioration.

  A strobe device according to the present invention comprises a capacitor for accumulating charges for causing a strobe to emit light, charging means for charging the capacitor each time the strobe is emitted, and a charging period and a non-charging period for the capacitor. Based on a determination means for determining a ratio of the charging period to a period, a ratio of the charging period, and a physical quantity that affects a charging power amount per unit time of the capacitor during the charging period, And a control means for controlling the charging start timing of the capacitor.

  By controlling the charging start timing in consideration of not only the charging period ratio but also the physical quantity that affects the charging power amount, it is possible to limit the appropriate charging operation adapted to changes in the charging power amount Become. That is, for example, even if the relationship between the amount of energy given to the heat generating component and the charging time changes, the charging start timing can always be kept appropriate.

  Specifically, for example, the control unit delays the charging start timing as the charging period ratio increases, and corrects the delay amount of the charging start timing according to the charging period ratio according to the physical quantity. good.

  By delaying the charging start timing as the ratio of the charging period increases, excessive charging operation is limited, and it is possible to prevent destruction or deterioration of a circuit or the like due to heat generation. At this time, even if the relationship between the amount of energy given to the heat generating component and the charging time is changed by correcting the delay amount of the charging start timing according to the ratio of the charging period according to the physical quantity, the delay amount of the charging start timing Can always be kept right.

  More specifically, for example, the control means sets the delay amount when the charge power amount per unit time decreases in response to the change in the physical quantity under the condition that the charge period ratio is constant. It is good to decrease.

  As a specific configuration, for example, the determination unit includes a counter that updates a count value between a predetermined first limit value and a second limit value, and the counter is set to the first limit value during the charging period. While updating the count value toward the second limit value during the non-charging period, the control means, as the count value approaches the first limit value, the count value The charging start timing may be delayed, and the update amount per unit time of the counter value during the charging period or the non-charging period may be changed according to the physical quantity.

  Alternatively, for example, the determination unit includes a counter that updates a count value between a predetermined first limit value and a second limit value, and the counter counts toward the first limit value during the charging period. While updating the value, the count value is updated toward the second limit value during the non-charging period, and the control means sets the count value between the first and second limit values. The charging start timing may be delayed or the delay amount of the charging start timing may be increased when the threshold value is closer to the first limit value than the threshold value, and the threshold value may be changed according to the physical quantity.

  A camera according to the present invention includes the strobe device.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the strobe device and camera which optimize the restriction | limiting of the charging operation for protecting a circuit etc. from destruction or deterioration.

1 is a schematic internal configuration diagram of a camera according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an internal configuration example of one frequency divider circuit illustrated in FIG. 1. It is a flowchart of a basic photographing operation. It is a flowchart of a basic photographing operation. It is a figure which shows the operation example of a charging circuit. It is a figure which shows the continuous light emission frequency dependence of the count value which concerns on basic imaging operation | movement. It is a figure which shows the dependence on the frequency | count of continuous light emission of the count value regarding three battery voltages regarding a basic imaging operation. It is a flowchart of the 1st improvement photography operation. It is a figure which shows the relationship between the delay amount of a battery voltage, the ratio of a charging period, and a charge start timing in connection with 1st-3rd improvement imaging | photography operation | movement.

  Hereinafter, an example of an embodiment of the present invention will be specifically described with reference to the drawings. In each of the drawings to be referred to, the same part is denoted by the same reference numeral, and redundant description regarding the same part is omitted in principle. In this specification, for simplification of description, a symbol or reference that refers to information, signal, physical quantity, state quantity, member, or the like is written to indicate information, signal, physical quantity, state quantity or Names of members and the like may be omitted or abbreviated.

  FIG. 1 is a schematic internal configuration diagram of a camera 1 according to an embodiment of the present invention. The camera 1 is provided with each part shown by FIG. The battery BAT is composed of a primary battery or a secondary battery, and outputs a voltage Vbat based on its own stored power. The charging circuit 12 formed as a boosting / charging circuit boosts the voltage Vbat and charges the capacitor 16 formed of an electrolytic capacitor or the like with the boosted voltage. The charging circuit 12 charges the capacitor 16 when the charging circuit 12 is on, and the charging circuit 12 stops charging the capacitor 16 when the charging circuit 12 is off. The voltage Vcc is a power supply voltage for driving the charging circuit 12. A terminal voltage of the capacitor 16 (hereinafter referred to as a charging voltage) is detected by the charging voltage detection circuit 14. The system controller 24 controls on / off of the charging circuit 12, and turns off the charging circuit 12 when the charging voltage detected by the circuit 14 reaches a predetermined specified value when the charging circuit 12 is on. .

  The strobe 20 formed of a xenon tube or the like emits light by the charge accumulated in the capacitor 16 when a trigger is generated from the trigger circuit 18. The light emission period of the strobe 20, that is, the light emission amount is controlled by the light emission control circuit 22. The trigger circuit 18 generates a trigger when a light emission command is supplied.

Each of the frequency dividing circuits 30 and 32 divides the reference clock output from the oscillator 34 to generate a divided clock having a frequency lower than the frequency of the reference clock. A frequency-divided clock from the frequency divider circuit 30 (hereinafter also referred to as a first frequency-divided clock) is supplied to the terminal T1, and a frequency-divided clock from the frequency-divided circuit 32 (hereinafter also referred to as a second frequency-divided clock) is supplied to the terminal T2. To be supplied. The frequency dividing circuit 30 outputs the first frequency-divided clock once every P ₁ seconds, and the frequency dividing circuit 32 outputs the second frequency-divided clock once every P ₂ seconds. .

The terminal T1 or T2 is alternatively connected to the counter 28 via the switch SW1. In the period for charging the capacitor 16, that is, the charging period, the controller 24 sets the counter 28 to the increment mode by connecting the switch SW1 to the terminal T1 and supplying the first frequency-divided clock to the counter 28. On the other hand, in the period in which the charging of the capacitor 16 is stopped, that is, in the non-charging period, the controller 24 connects the switch SW1 to the terminal T2 and supplies the second divided clock to the counter 28, thereby setting the counter 28 in the decrement mode. Set to. In the increment mode, the counter 28 is incremented in response to the first divided clock, and in the decrement mode, the counter 28 is decremented in response to the second divided clock. As a result, the count value of the counter 28 is incremented every P ₁ seconds (that is, increased by 1) in response to the first frequency-divided clock from the frequency dividing circuit 30 in the charging period, and is divided in the non-charging period. It is decremented every P ₂ seconds (ie, decreased by 1) in response to the second divided clock from the frequency circuit 32. The number of bits of the count value of the counter 28 is arbitrary, and the count value takes a value between a predetermined lower limit value and an upper limit value. Here, it is assumed that the count value of the counter 28 is represented by 8 bits, and the lower limit value and the upper limit value are “0” and “255”, respectively.

  When the exposure command is given, the imaging unit 36 performs photoelectric conversion on the optical image of the object scene (subject) to generate an image signal. The signal processing circuit 38 evaluates the luminance of the image signal output from the imaging unit 36 when the luminance evaluation command is given, and compresses the image signal output from the imaging unit 36 when the recording command is given. To record on the recording medium 40.

  The battery voltage detection unit 44 includes an A / D converter that digitizes an analog voltage signal indicating the output voltage Vbat of the battery BAT, detects the output voltage Vbat of the battery BAT, and gives a detection result to the controller 24.

The frequency dividing circuits 30 and 32 can be formed so that at least one of P ₁ seconds and P ₂ seconds, which are output periods of the first and second frequency-divided clocks, is variable. Here, consider a case where the frequency dividing circuit 30 is formed so that P ₁ sec is variable. FIG. 2 shows an internal configuration of the frequency dividing circuit 30. The frequency dividing circuit 30 includes n frequency dividers 30 [1] to 30 [n]. n is an arbitrary integer of 2 or more. Each of the frequency dividers 30 [1] to 30 [n] divides the reference clock output from the oscillator 34 to generate and output a divided clock having a frequency lower than the frequency of the reference clock. However, the frequency of the divided clock generated by the frequency divider is different between the frequency dividers 30 [1] to 30 [n]. The controller 24 selects any one of the frequency dividers 30 [1] to 30 [n] as a target frequency divider, and is a switch interposed between the frequency dividers 30 [1] to 30 [n] and the terminal T1. By controlling the SW3, the target frequency divider is connected to the terminal T1. By changing the target frequency divider between the frequency dividers 30 [1] to 30 [n], the cycle of the first frequency-divided clock changes.

  Hereinafter, the photographing operation accompanied by the flash 20 will be described. A control program for realizing each of the following photographing operations can be stored in the flash memory 42.

[Basic shooting operation]
First, the basic photographing operation will be described with reference to FIGS. The controller 24 performs an operation according to the flow of FIGS. In the basic photographing operation, it is assumed that P ₁ seconds and P ₂ seconds (that is, the periods of the first and second divided clocks) are fixed.

  First, in step S1, a predetermined initial value is set as the count value of the counter 28. Here, it is assumed that the initial value is 48. Thereafter, in steps S3 and S5, the controller 24 switches the charging circuit 12 from OFF to ON to start charging the capacitor 16, and connects the switch SW1 to the terminal T1 to set the counter 28 in the increment mode. As a result, the charging period is started and the increment of the counter 28 in response to the first divided clock is started.

  Thereafter, in step S7, the controller 24 compares the charging voltage detected by the charging voltage detection circuit 14 with a specified value, and when the charging voltage reaches the specified value, causes the transition to step S9 to occur. And the process of S11 is performed. In steps S9 and S11, the controller 24 switches the charging circuit 12 from on to off to stop charging the capacitor 16, and connects the switch SW1 to the terminal T2 to set the counter 28 to the decrement mode. As a result, the charging period is ended and the non-charging period is started, and the increment of the counter 28 is ended and the counter 28 is decremented in response to the second divided clock.

  When the charging of the capacitor 16 is completed, that is, when the processing of steps S9 and S11 is completed and the processing reaches step S13, the user can operate the shutter button 26. When a predetermined operation is input to the shutter button 26, a transition from step S13 to step S15 occurs. In step S15, the brightness of the object scene (subject) is measured by a TTL (through the lens) method. Specifically, an exposure command and a luminance evaluation command are given from the controller 24 to the imaging unit 36 and the signal processing circuit 38, respectively, and the brightness of the object scene (subject) is detected by the signal processing circuit 38 based on the output image signal of the imaging unit 36. Is measured.

  Thereafter, in step S17, the controller 24 calculates the optimum light emission amount of the strobe 20 based on the measurement result in step S15, and sets the light emission stop timing corresponding to the calculated optimum light emission amount in the light emission control circuit 22. In a succeeding step S19, a recording process (imaging recording process) is executed. Specifically, the controller 24 gives a light emission command to the trigger circuit 18, gives an exposure command to the imaging unit 36, and gives a recording command to the signal processing circuit 38. As a result, an image signal of the object scene (subject) exposed to the light emitted from the strobe 20 having the optimum light emission amount is output from the imaging unit 36, and the signal processing circuit 38 compresses the output image signal in a compressed state. Recording is performed on the recording medium 40.

  After step S19, the controller 24 performs standby control processing including steps S21, S23, S25, S27, S29, and S31. After the standby control process, the process returns to step S3 in FIG. In steps S21, S23, and S25, the count value of the counter 28 is compared with predetermined threshold values TH1, TH2, and TH3, respectively. “0 <TH1 <TH2 <TH3 <255” is satisfied. Here, it is assumed that TH1 = 96, TH2 = 128, and TH3 = 192. When the count value is less than the threshold value TH1, the process directly returns to step S3. When the count value is greater than or equal to the threshold value TH1 and less than the threshold value TH2, the process returns to step S3 after waiting for 1 second in step S27. When the count value is greater than or equal to the threshold value TH2 and less than the threshold value TH3, the process waits for 2 seconds in step S29 and then returns to step S3. When the count value is equal to or greater than the threshold value TH3, the process waits for 4 seconds in step S31 and then returns to step S3.

  Referring to FIG. 5, charging of capacitor 16 is started by turning on charging circuit 12. The time required to increase the terminal voltage of the capacitor 16 from 0 V to the specified value is 2.0 seconds, and the charging circuit 12 is turned off when 2.0 seconds have elapsed from the start of charging. When the shutter button 26 is operated after the charging is completed, the photometry and recording process is executed over a period of 2.5 seconds. When the recording process is completed, the charging of the capacitor 16 is resumed after the waiting time corresponding to the count value of the counter 28 has elapsed. However, the period required for the second and subsequent charging depends on the amount of charge remaining in the capacitor 16. That is, the smaller the amount of light emitted from the strobe 20, the more charge remains in the capacitor 16 and the next charging period becomes shorter.

  A period composed of a charging period and a non-charging period is referred to as an entire period. The count value of the counter 28 increases as the ratio of the charging period to the entire period (hereinafter simply referred to as the ratio of the charging period) increases, and the ratio of the non-charging period to the entire period (hereinafter simply referred to as the ratio of the non-charging period) increases. Get smaller. The standby time from the completion of the recording process to the resumption of the charging period is extended in the order of 0 second → 1 second → 2 seconds → 4 seconds as the count value increases, and charging of the capacitor 16 starts after the strobe 20 emits light. The timing (hereinafter also referred to as the charging start timing or simply the charging start timing of the capacitor 16) is delayed due to the extension of the standby time.

When the shutter button 26 is frequently operated, the ratio of the charging period is gradually increased, and accordingly, the standby time is extended stepwise. Due to the extension of the standby time, the charging start timing of each time is delayed, and the ratio of the non-charging period is increased. As a result, the ratio of the charging period reaches a certain value. That is, when photographing with full light emission of the strobe 20 is repeatedly executed, the count value changes along the polygonal line G1 in FIG. In polygonal line G1, (similarly even polygonal lines G2 and G3 of FIG. 7 described later) which assumes that that P ₁ sec 0.2 sec and P ₂ seconds is fixed to 0.5 sec.

  According to the polygonal line G1, the count value reaches “96” when the photographing is performed about 20 times in the continuous photographing process in which the strobe 20 is fully lit, and the standby time is changed from “0 second” to “1”. "Seconds". When photographing is performed about 30 times, the count value reaches “128”, and the standby time is updated from “1 second” to “2 seconds”. The count value indicates a value in the vicinity of “192” when the number of shootings exceeds 90, and the standby time varies between “2 seconds” and “4 seconds”.

  As can be understood from the above description, the strobe 20 emits light by the electric charge accumulated in the capacitor 16. The capacitor 16 is charged by the charging circuit 12 every time the strobe 20 emits light. The controller 24 uses the counter 28 to determine the ratio between the charging period and the non-charging period of the capacitor 16 and delays the next charging start timing of the capacitor 16 as the charging period ratio increases. By delaying the charging start timing of the capacitor 16, excessive charging operation is limited, and destruction or deterioration of the circuit or the like due to heat generation can be prevented.

Meanwhile, in the charging period, the charging circuit 12 converts the input power, which is the product of the primary side voltage Vbat and the current Ibat, into output power with the efficiency η, and supplies the output power to the capacitor 16. Therefore, the energy supplied per unit time to the capacitor 16 during the charging period, that is, the charging electric energy E per unit time of the capacitor 16 during the charging period is expressed by the following formula (1). Ibat represents a supply current from the battery BAT to the charging circuit 12 during the charging period. Vcap represents the terminal voltage of the capacitor 16. Icap represents the charging current to the capacitor 16 (current between the charging circuit 12 and the capacitor 16 in the direction of charging the capacitor 16).
E = Vbat × Ibat × η
= Vcap × Icap (1)

  Therefore, when the primary side voltage Vbat decreases due to the consumption of the battery BAT or the like, assuming that the primary side current Ibat and the efficiency η are constant, the charging power amount E per unit time decreases. If it does so, compared with the case where this fall does not exist, required charging time becomes long and a count value becomes large. An increase in the count value results in delaying the charging start timing. That is, when the primary side voltage Vbat decreases, the charging start timing is delayed more than necessary even though there is no change in the total amount of power required for charging.

  A broken line G1 in FIGS. 6 and 7 represents the dependency of the count value on the number of times of continuous light emission when the primary voltage Vbat matches a certain reference voltage. On the other hand, the polygonal lines G3 and G5 in FIG. 7 represent the dependency of the count value on the number of times of continuous light emission when the primary side voltage Vbat matches the first and second reduced voltages, respectively. Here, the first drop voltage (for example, 4V) is lower than the reference voltage (for example, 5V), and the second drop voltage (for example, 3V) is further lower than the first drop voltage.

  According to the polygonal line G3, the count value reaches “96” when the photographing is performed about 15 times in the continuous photographing process in which the flash 20 performs full light emission, and the standby time is changed from “0 second” to “1”. "Second", and when the number of shots is about 20 times, the count value reaches "128", the standby time is updated from "1 second" to "2 seconds", and the number of shots exceeds 40 The count value indicates a value in the vicinity of “192”, and the waiting time changes between “2 seconds” and “4 seconds”. According to the polygonal line G5, in the process of continuous shooting in which the flash 20 is fully lit, the count value reaches “96” when the shooting is performed about eight times, and the standby time is changed from “0 second” to “1”. "Second", the count value reaches "128" when shooting is performed about 12 times, the standby time is updated from "1 second" to "2 seconds", and the number of shots exceeds 20 The waiting time is fixed at “4 seconds” after the count value exceeds “192”.

  In this way, when no change in the primary side voltage Vbat is taken into consideration, the influence of heat generation does not change, but a large delay (delay of charging start timing) occurs with a small number of times of light emission, resulting in poor usability. A technique for improving this will be described in each improved photographing operation described later.

[First improvement shooting operation]
The first improved shooting operation will be described. In the first improved photographing operation, the configuration of FIG. 2 is used, and the period of the first divided clock (that is, P ₁ second) is changed according to the primary side voltage Vbat.

First, specific numerical examples regarding the change will be given. Here, it is assumed that the primary side current Ibat and the efficiency η are constant. When the primary side voltage Vbat is 5 V (volts), the time required to increase the terminal voltage of the capacitor 16 from 0 V to the specified value (hereinafter referred to as full charge time) is 2.0 seconds, and P Assume that ₁ second is set to 0.2 seconds. Then, when the primary side voltage Vbat is 5V, the increment of the count value corresponding to the full charge time is “10”.

Even when the primary side voltage Vbat falls below 5V, the controller 24 sets the primary side voltage Vbat so that the increment of the count value corresponding to the full charge time becomes “10” or approaches “10”. Accordingly, P ₁ second is controlled. For example, when the primary side voltage Vbat is 4V, the full charge time is 2.5 seconds (= 2 seconds × 5V / 4V). Therefore, P ₁ second is set to 0.25 seconds, and the primary side voltage Vbat is When it is 3 V, the full charge time is about 3.3 seconds (≈2 seconds × 5 V / 3 V), so P ₁ second is set to about 0.33 seconds. In order to achieve this (see FIG. 2), the frequency of the divided clocks from the frequency dividers 30 [1], 30 [2] and 30 [3] are 0.2 seconds, 0.25 seconds and about respectively. The frequency dividing circuit 30 is formed so as to be 0.33 seconds, and the switch SW3 may be controlled according to the primary side voltage Vbat.

As described above, the number n of the frequency dividers forming the frequency divider circuit 30 is arbitrary as long as it is 2 or more. By increasing the number n, P ₁ seconds can be changed more finely. The number n may be determined according to the required number of changes in P ₁ second.

FIG. 8 is a flowchart of the first improved photographing operation. The flowchart of the operation after a predetermined operation is input to the shutter button 26 is the same as FIG. Regarding the matters not specifically mentioned, the flowchart of the first improved photographing operation is the same as that of the basic photographing operation, and differences from the basic photographing operation will be described below. In the first improved photographing operation, P ₂ seconds (that is, the period of the second divided clock) is fixed, while P ₁ seconds (that is, the period of the first divided clock) is made variable.

After step S1, the adaptive setting process of step S2 is executed before step S3. In the adaptive setting process of step S2, the voltage Vbat is detected by the battery voltage detection unit 44, and the controller 24 controls the switch SW3 according to the detection voltage Vbat. Now, assume that when Vbat = Vbat _A (for example, 5 V), P ₁ seconds is set to P _1A seconds (for example, 0.2 seconds). In this case, if a voltage Vbat that matches Vbat _B (for example, 4 V) is detected through the power consumption of the battery BAT, P ₁ seconds are changed to P _1B seconds (for example, 0.25 seconds) in step S2. . At this time, (Vbat _B × P _1B) than the (Vbat _B × P _1A) so close to (Vbat _A × P _1A), preferably (Vbat _B × P _1B) is (Vbat _A × P _1A) SW3 may be controlled so as to match.

  After the process of step S2, the standby control process of FIG. 4 is performed through the processes of steps S3, S5, S7, S9, S11, S13, S15, S17, and S19. After the standby control process, the process returns to step S2.

[Second improved shooting operation]
The second improved shooting operation will be described. You may make it change the period (namely, P ₂ second) of a _2nd frequency-divided clock according to the primary side voltage Vbat. In this case, the frequency dividing circuit 32 has the same configuration as that of the frequency dividing circuit 30 of FIG. 2, and the period of the second frequency-divided clock supplied from the frequency dividing circuit 32 to the terminal T2 is made variable. Then, the controller 24 may change the period of the second divided clock (that is, P ₂ seconds) by controlling the switch in the frequency dividing circuit 32 in accordance with the primary side voltage Vbat. The flowchart of the second improved shooting operation is the same as that of the first improved shooting operation (that is, the flowcharts of FIGS. 8 and 4). However, in the adaptive setting process in step S2, the cycle of the second divided clock is set or changed according to the primary side voltage Vbat. When a decrease in the primary side voltage Vbat is observed, P ₂ seconds may be shortened in comparison with that before the decrease.

Further, the frequency dividing circuits 30 and 32 are formed so that the periods of the first and second frequency-divided clocks are individually variable, and both the first and second frequency-divided clocks are changed according to the primary side voltage Vbat. It may be variably set. That is, the first and second improved photographing operations may be combined, and in the adaptive setting process in step S2, at least one of P ₁ second and P ₂ seconds may be set or changed according to the primary side voltage Vbat. When a decrease in the primary side voltage Vbat is observed, an increase in P ₁ seconds or a decrease in P ₂ seconds may be executed in comparison with the previous decrease, or an increase in P ₁ seconds and P ₂ What is necessary is just to carry out the reduction of seconds.

[Third improved shooting operation]
The third improved photographing operation will be described. Instead of variably setting the _second or P ₂ seconds P in accordance with the primary-side voltage Vbat, it may be a threshold TH1~TH3 response to the primary side voltage Vbat is variably set. The flowchart of the third improved shooting operation is also the same as that of the first improved shooting operation (that is, the flowcharts of FIGS. 8 and 4). However, in the adaptive setting process of step S2, the threshold values TH1 to TH3 are set or changed according to the primary side voltage Vbat. When a decrease in the primary side voltage Vbat is observed, the thresholds TH1 to TH3 may be increased in comparison with that before the decrease. For example, if TH1 = 70, TH2 = 100, and TH3 = 230 when the voltage Vbat is 5V, TH1 = 100, TH2 = 145, and TH3 when the voltage Vbat reaches 4V. = 250.

The first or second improved shooting operation may be combined with the third improved shooting operation. That is, the setting or changing target in the adaptive setting process may further include P ₁ second and / or P ₂ second in addition to the threshold values TH1 to TH3.

[Discussion and modification]
While considering the basic photographing operation and the first to third improved photographing operations, some modified examples will be described.

  In the basic photographing operation, the charging start timing of the capacitor 16 after the strobe 20 emits light is delayed as the charging period ratio increases. In the first to third improved photographing operations, the charging power amount E per unit time of the capacitor 16 (hereinafter referred to as charging power amount E per unit time) during the charging period is constant (that is, for example, the voltage Vbat is Under certain conditions), the charging start timing is delayed as the charging period ratio increases. However, in the first to third improved photographing operations, the charging start timing is controlled based not only on the ratio of the charging period but also on the physical quantity Q (eg, voltage Vbat) that affects the charging power amount E per unit time. ing. At this time, the delay amount DL of the charging start timing according to the charging period ratio is corrected according to the physical quantity Q.

FIG. 9 shows the state of the correction. Now, in the state where the voltage Vbat is 5 V, when the charge period ratio is R _A (eg, 30%), the delay amount DL is DL _A (eg, 1 second), and the charge period ratio is R _B ( For example, it is assumed that the delay amount DL is DL _B (for example, 2 seconds). Here, “R _A <R _B ” and therefore “DL _A <DL _B ”. Note that the delay amount DL may be considered as an average value of the standby time given to the charging start timing in the standby control process when a continuous operation under a predetermined condition is given to the shutter button 26, for example.

In this case, when the voltage Vbat drops 4V, the ratio of the charging period even R _B, delay DL is small DL _B 'than DL _B instead DL _B (e.g. 1 second). For example, DL _A = DL _B '. That is, when the charge power amount E per unit time is reduced in response to the decrease in the voltage Vbat under the condition that the charge period ratio is constant (R _B ), the delay amount DL corresponding to the charge period ratio is set to Decrease (see curve 301 with arrow).

From another viewpoint, when the charging period ratio increases from R _A to R _B under the condition that the charging energy E per unit time is constant, the delay amount DL increases from DL _A to DL _B. On the other hand (see curve 302 with an arrow), even if the ratio of the charging period increases from R _A to R _B , if the voltage Vbat decreases from 5 V to 4 V and the charging energy E per unit time decreases. The delay amount DL is not increased, or the increase amount of the delay amount DL is made smaller than (DL _B −DL _A ) (see the curve 303 with an arrow).

  Even when the physical quantity Q changes as a result of the correction to the delay amount DL (for example, even when Vbat decreases), the dependency of the count value on the number of continuous light emission times can be maintained as the broken line G1 in FIG. Or it can be close to the polygonal line G1. That is, the problem that a larger delay (a delay in charging start timing) occurs with a small number of light emission times even though the influence of heat generation does not change is solved, and an accurate charging operation adapted to the change in the charging power amount E is restricted. It becomes possible. That is, even if the relationship between the amount of energy given to the heat generating component and the charging time changes, an appropriate delay can always be given to the charging start timing.

  The voltage Vbat is an example of the physical quantity Q. The physical quantity Q may be other than the voltage Vbat, and may include, for example, the primary current Ibat. In the first to third improved imaging operations described above, it is assumed that the current Ibat is constant, but the current Ibat may change. For example, when the voltage Vbat decreases considerably due to the consumption of the battery BAT, the internal resistance of the battery BAT becomes considerably high. At this time, if a large current Ibat is extracted from the battery BAT, the voltage Vbat falls below the lower limit of the predetermined operating range, and the camera 1 cannot be driven. In order to avoid this, for example, the controller 24 sets the current Ibat when the remaining capacity or open voltage value of the battery BAT is less than a predetermined value, compared to when the remaining capacity or open voltage value of the battery BAT is equal to or higher than a predetermined value. Can be lowered. Alternatively, for example, the controller 24 can increase the current Ibat more than usual for quick charging, if necessary.

As described above, when it is assumed that the current Ibat is not constant, a current detection unit (not shown) for detecting the current Ibat is provided, and the detected value of the current Ibat may be given to the controller 24. When the controller 24 adopts a configuration that specifies the current Ibat, the current detection unit may be unnecessary. Alternatively, the controller 24 may recognize a change in the current Ibat based on the control content of a block (not shown) that controls the current value of the current Ibat. Event, the adaptive setting process in step S2 any, the controller 24 in accordance with the current Ibat, P ₁ second may be set or changed P ₂ seconds and / or threshold TH1～TH3.

The physical quantity Q may include a secondary-side voltage Vcap and a current Icap. Based on the detection result of the voltage Vcap by the charging voltage detection circuit 14 and the detection result of a current detection unit (not shown) that detects the current Icap that can be provided in the camera 1, the controller 24 calculates the charging energy E per unit time. Can be derived. Thus, the adaptive setting process in step S2, the controller 24, depending on its derivation result, P ₁ second may be set or changed P ₂ seconds and / or threshold TH1～TH3.

  It can be said that the camera 1 includes a determination unit that determines the ratio of the charging period. In the present embodiment, the determination unit is a counter that updates a count value between a predetermined first limit value and a second limit value. 28 is included. The counter 28 updates the count value toward the first limit value based on the first divided clock during the charging period, and counts toward the second limit value based on the second divided clock during the non-charging period. Update the value.

The controller 24 delays the charging start timing as the count value approaches the first limit value. Then, the controller 24 can change the update amount per unit time of the counter value during the charging period or the non-charging period according to the physical quantity Q, thereby eliminating the above problem. In the first or second improved photographing operation, the update amount is changed by changing the P ₁ second or the P ₂ second.

  The controller 24 delays the charging start timing when the count value is closer to the first limit value than the threshold value (TH1, TH2, or TH3) set between the first and second limit values, The delay amount of the charge start timing when the start timing is delayed is increased. At this time, the controller 24 can change the threshold value according to the physical quantity Q as in the third improved photographing operation, and this can also solve the above problem.

In the above description, it is assumed that the efficiency η is constant, but in an actual circuit, the efficiency η can change depending on the voltage and current on the primary side and the secondary side of the charging circuit 12. Therefore, table data that defines the relationship between Vbat, Ibat, Vcap, or Icap and efficiency η is prepared in advance, and all or a part of the detection results of Vbat, Ibat, Vcap, and Icap and the table data are also stored. It may be used to set P ₁ second, P ₂ second, or threshold values TH1 to TH3.

  In the present embodiment, three thresholds TH1 to TH3 are used as thresholds for setting the delay amount of the charging start timing. However, the number of thresholds may be any number as long as it is 1 or more.

  In the present embodiment, since the counter 28 is incremented during the charging period and the counter 28 is decremented during the non-charging period, the first limit value is the upper limit value “255” and the second limit value is the lower limit value “ However, the counter 28 may be decremented during the charging period and incremented during the non-charging period. In this case, the first limit value is set to the lower limit value “0”, the second limit value is set to the upper limit value “255”, and the standby control process in FIG. 4 is also appropriately corrected. Of course, the number of bits of the count value of the counter 28 may be other than eight.

  In this embodiment, the first / second divided clock is counted by the hardware counter. However, the first / second divided clock may be counted by the software counter prepared in the controller 24. Good. In this case, the count value is incremented or decremented by interrupt processing.

  The embodiment of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims. The above embodiment is merely an example of the embodiment of the present invention, and the meaning of the term of the present invention or each constituent element is not limited to that described in the above embodiment. The specific numerical values shown in the above description are merely examples, and as a matter of course, they can be changed to various numerical values. Although the present invention has been described with reference to the camera 1 as a digital camera, the present invention can also be applied to a silver salt film camera. The camera 1 has a strobe device. It may be considered that any part related to strobe emission among the parts shown in FIG. 1 forms a strobe device.

  The target device that is the camera 1 or the strobe device can be configured by hardware such as an integrated circuit or a combination of hardware and software. Arbitrary specific functions that are all or part of the functions realized by the target device are described as a program, the program is stored in the flash memory 42, and the program is executed by a program execution device (for example, the target device). The specific function may be realized by executing the program on a controller 24) including a microcomputer that can be mounted on the computer. The program can be stored and fixed on an arbitrary recording medium. The recording medium for storing and fixing the program may be mounted or connected to a device (such as a server device) different from the target device.

1 Camera 12 Charging Circuit 16 Capacitor 20 Strobe 24 System Controller 28 Counter

Claims (6)

A capacitor for accumulating charges for causing the strobe to emit light;
Charging means for charging the capacitor each time the strobe light is emitted;
A discriminating means for discriminating a ratio of the charging period to a total period including a charging period and a non-charging period of the capacitor;
Control means for controlling the charging start timing of the capacitor after the strobe light emission based on the ratio of the charging period and a physical quantity that affects the charging power amount per unit time of the capacitor during the charging period; A strobe device characterized by comprising: The control means delays the charging start timing as the charging period ratio increases, and corrects the delay amount of the charging start timing according to the charging period ratio according to the physical quantity. Item 2. The strobe device according to item 1. The control means reduces the delay amount when the charging power amount per unit time decreases in response to the change in the physical quantity under the condition that the charging period ratio is constant. The strobe device according to claim 2. The determination means includes a counter that updates a count value between a predetermined first limit value and a second limit value,
The counter updates the count value toward the first limit value during the charge period, while updating the count value toward the second limit value during the non-charge period;
The control means delays the charging start timing as the count value approaches the first limit value, and sets an update amount per unit time of the counter value during the charging period or the non-charging period. The strobe device according to any one of claims 1 to 3, wherein the strobe device is changed in accordance with a physical quantity. The determination means includes a counter that updates a count value between a predetermined first limit value and a second limit value,
The counter updates the count value toward the first limit value during the charge period, while updating the count value toward the second limit value during the non-charge period;
The control means delays the charge start timing when the count value is closer to the first limit value than a threshold value set between the first and second limit values, or sets a delay amount of the charge start timing. The strobe device according to claim 1, wherein the strobe device is increased and the threshold value is changed according to the physical quantity. A camera comprising the strobe device according to any one of claims 1 to 5.

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